Question

salamander dichotomous key
suppose you find a large colorful salamander while walking near a pond. the salamander has already been named and classified, but how can you learn to identify it? as an aid to help others identify unknown organisms, biologists have developed classification keys. these classification keys are often called dichotomous keys (the word dichotomous comes from the word dichotomy meaning \two opposite categories\). a dichotomous key presents the user with two opposite statements about some trait of an organism. by choosing one of the two statements that best describes the unknown organism, the user is lead to further pairs of statements. by going from one set of statements to another, the name of the organism or its classification group is determined.
pre - lab questions:

1. how many choices does a dichotomous key provide at each step? two choices
2. what are some of the differences you see among the salamanders illustrated? color size, presence of spots, body shape tail length.

procedure:
use the dichotomous key provided on the back of this sheet to identify at least 8 species of salamanders (in addition to the two we will work through as a class). begin by reading statements 1a and 1b. one of the statements describes the salamander; the other statement does not. follow the directions for the statement that applies to that salamander and continue following the correct statements until you have identified it. record the scientific and common names of the salamander in the data table below.

1. repeat step 2 for each of the other salamanders in figure 1.

data table:
scientific name common name

1. __________ __________
2. __________ __________
3. __________ __________
4. __________ __________
5. __________ __________
6. __________ __________
7. __________ __________
8. __________ __________
9. __________ __________
10. __________ __________
11. __________ __________

post - lab questions: answer the following using complete thoughts.

1. as you used the classification key to identify the salamanders, did the characteristics you used start out general and become more specific, or did you start with specific characteristics that became more general? the characteristics started general and became more specific.
2. what two names make up the scientific name of each salamander? genus name and species name.

Explanation:

1. A dichotomous key provides two choices at each step as it is based on the concept of dichotomy (two opposite categories).
2. Differences among salamanders can include coloration (presence of spots), body - shape, and tail - length as these are observable physical traits.
3. When using a classification key, characteristics often start general and become more specific to narrow down the identification of the organism.
4. The two names of each salamander are the scientific name (binomial nomenclature with genus and species) and the common name.

Answer:

1. Two choices
2. Coloration (presence of spots), body - shape, tail - length
3. The characteristics started general and became more specific.
4. Scientific name and common name